Visibility modifiers (public, private, internal, external) in Blockchain / Solidity - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to make the function accessible from anywhere.

Blockchain / Solidity

function greet() [1] returns (string memory) {
    return "Hello!";
}

Drag options to blanks, or click blank then click option'

Aprivate

Bpublic

Cinternal

Dexternal

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'private' makes the function inaccessible from outside the contract.

Using 'internal' restricts access to the contract and its children only.

The public visibility modifier allows the function to be called from anywhere, both inside and outside the contract.

2fill in blank

medium

Complete the code to make the variable accessible only within the contract and derived contracts.

Blockchain / Solidity

uint256 [1] myNumber;

Drag options to blanks, or click blank then click option'

Ainternal

Bprivate

Cpublic

Dexternal

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'public' exposes the variable to everyone.

Using 'private' restricts access only to the contract itself.

The internal modifier restricts access to the contract itself and any contracts that inherit from it.

3fill in blank

hard

Fix the error in the function declaration to allow it to be called only from outside the contract.

Blockchain / Solidity

function externalCall() [1] {
    // function logic
}

Drag options to blanks, or click blank then click option'

Aexternal

Bprivate

Cpublic

Dinternal

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'public' allows both internal and external calls.

Using 'private' restricts calls to inside the contract only.

The external modifier means the function can only be called from outside the contract, not from inside.

4fill in blank

hard

Fill both blanks to create a private variable and a public function to access it.

Blockchain / Solidity

uint256 [1] secretNumber;
function getSecret() [2] view returns (uint256) {
    return secretNumber;
}

Drag options to blanks, or click blank then click option'

Aprivate

Bpublic

Cinternal

Dexternal

Attempts:

3 left

💡 Hint

Common Mistakes

Making the variable public exposes it directly.

Making the function private or internal hides it from external callers.

The variable is private so it can't be accessed directly outside the contract. The function is public so anyone can call it to get the value.

5fill in blank

hard

Fill all three blanks to define an internal variable, a private function, and a public function that calls the private one.

Blockchain / Solidity

uint256 [1] data;


function calculate() [2] view returns (uint256) {
    return data * 2;
}


function getResult() [3] view returns (uint256) {
    return calculate();
}

Drag options to blanks, or click blank then click option'

Ainternal

Bprivate

Cpublic

Dexternal

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'public' for the private function exposes it.

Using 'private' for the public function hides it from outside.

The variable is internal so accessible inside the contract and children. The private function can only be called inside this contract. The public function allows anyone to call it and get the result.